Process for rapid bleaching



:K3-1 n 7 s R I Em @www www P19850@ XR 3937015111 Feb. 27, 1968 T. E.WESTALL. 3,370,911

PROCESS FOR RAPID BLEACHING Filed oct. 21, 1964 e sheets-sheet 1 E Q nCz O k U M q. N n

C N 2N fg f! E' Og *L -4 om SQ N sg S S INVENTOR. ik 7/70/445 'D/So/yh/fsr/)LL Q Q BY v` bb www@ Feb. 27, 1968 T. E. WESTALL 3,370,911

PROCESS FOR RAPID BLEACHING Filed oct. 21, 1964 e sheets-sheet 2 www W li 1 22A i @lo 5 N INVENTOR. W WOM/qfo/so/v /SSMLL v a,

Feb. 27, 1968 T. f-:.wEsTA1 1 PROCESS FOR RAPID BLEACHING G Sheets-SheetFiled OCC. 2l, 1964 T. EWESTALL 3,370,911

PROCESS FOR RAPID BLEACHING Feb. 27, 1968 G Sheets-Sheet 4 Filed 001,.21, 1964 R O T. N E V W Feb. 27, 1968 T. E. wEsTALL PROCESS FOR RAPIDBLEACHING 6 Sheets-Sheet 5 N m7,/ ArrOfQ'YYS Filed OO. 21, 1964 Feb. 27,'1968 T. E. WESTALL 3,370,911

PROCESS FOR RAPID BLEACHING Filed oct. 21, 1964 v e sheets-sheet e i. E.4L

EN n s 53" 5% l LO/i A a l. I ,s @Il l@ ZZ n INVENTOR. 717/0145 mso/yMisma BYMW Arrows/6X5 United States Patent 3,370,911 PROCESS FOR RAPIDBLEACHING Thomas E. Westall, Marion, N.C., assignor to The AmericanThread Company, New York, N.Y., a corporation of New Jersey Filed Oct.21, 1964, Ser. No. 405,430 12 Claims. (Cl. 8-111) ABSTRACT 0F THEDISCLOSURE This invention is directed to a combined and continuousmercerizng and bleaching process for yarn, which is carried out in ashort period of time. The yarn moves forward continuously through thefollowing major process steps: boiling out, mercerizng (caustic),caustic washing, steaming, bleaching, steaming, washing and finishing.

This invention relates to processes for the mercerization and bleachingof cotton yarn, and more particularly to a combined mercerization andbleaching process in which the steps of mercerization and bleaching arecarried out in a single operation while a Warp of yarn is being advancedcontinuously.

Prior to the present invention it has been customary to mercerize andbleach yarn in separate operations. The yarn is mercerized in acontinuous process, dried, and then bleached in a batch-wise operation.

Unmercerized and unbleached yarn is received in the form of spools orcones, each having a single end of yarn. These ends are brought togetherfrom a plurality of spools to form a ball of warp, in which the ends aresubstantially parallel. Typically, 378 ends are brought together in thismanner. A plurality of warps, for example 12 to 48 warps, are passedsimultaneously through the steps of the present process. The yarn ispassed from the balls of warp through the mercerizng process. Inmercerizng, the ends are separated from one another as they are pulledfrom the ball of warp so that each warp of 378 ends passes into the-mercerizing process along a horizontal plane. These warps are firstpassed through boiling water to remove grease and foreign matter in astep which is commonly known as boiling out. The yarn then advances intoan aqueous caustic solution, which typically contains about by weight ofcaustic soda. Causticization is followed by a plurality of washings atvarious elevated temperatures. Squeeze rollers or nip rollers controlthe amount of liquid carried over from one treatment to the next. Afterthe last washing cycle the warps are dried in a steam heated dryer andare piled on pallets.

Bleaching of yarn according to prior practice is carried out startingwith dried mercerized yarn treated as described above. Warps of driedyarn are transferred from the pile to a bleaching tank, which ispreferablyl a covered rectangular tank containing hot aqueous bleachingsolution. The yarn is spread out in layers, one above the other, in thetank to afford good contact between the yarn and the bleaching solution.Various aqueous alkaline bleaching solutions can be used; a preferredbleaching solution comprises hydrogen peroxide, sodium silicate, andsodium hydroxide dissolved in water. The yarn remains in the bleachingtank several hours. Following bleaching, the yarn is transferred to atank, then washed to remove alkali carried out by the yarn, and is thendried. The dried warp is again formed into a pile resting on a pallet.

It can be seen that the former practice of mercerizng 3,370,911 PatentedFeb. 27, 1968 rice and bleaching in separate operations involved a largenumber of steps. Handling of the yarn is complicated by the fact that itis necessary to take a pile of mercerized yarn, unwind it for bleaching,and then again form a pile after bleaching is concluded.

One object of this invention is to provide a continuous bleachingprocess.

Another object of this invention is to provide a combined mercerizationand bleaching process which results in a considerable reduction in thenumber of steps required in order to obtain a mercerized and bleachedyarn.

A further object of this invention is to provide a bleaching processwhich is more rapid than prior bleaching processes.

A further object of this invention is to provide an apparatus forcombined mercerization and bleaching.

A still further object of this invention is to provide a novel steamingchamber for heating the yarn after it has contacted the bleachingsolution and thereby make bleaching more rapid and effective.

These and other objects will be apparent from the .description whichfollows.

FIG. 1 is a flow sheet showing diagrammatically' the process steps ofthis invention;

FIG. 2A is a schematic diagram of the first part of the process;

FIG. 2B is a schematic diagram of the remainder of the process;

FIG. 3 is a side elevation of the first steam chamber;

FIG. 4 is a front section of the first steam heating chamber;

FIG. 5 is a perspective lview of a portion of the bottom wall of thefirst steam heating chamber, with parts broken away, showing theentrance opening for warps of yarn in detail;

FIG. 6 is a perspective view of the bleaching tank, with parts removedand parts shown in section, and with the reagent feed conduits showndiagrammatically;

FIG. 7 is a front elevational view, with parts lbroken away and partsshown in section, of the bleaching tank and second steam heatingchamber;

FIG. 8 is a cross section taken along line 8-8 of FIG. 7 showing aroller in the second steam heating chamber and a clutch drive mechanismtherefor in detail; and

FIG. 9 is a side sectional view of a flexible curtain seal for a steamheating chamber.

Referring now to FIG. 1, the yarn ends from a plurality of warps arebrought together to form a sheet 10. The yarns in the sheet are disposedin parallel side-by-side relationship in a single plane, so that thewarp from a distance has the appearance of a thin continuous tape orsheet of indefinite length.

T'he warps are passed through the entire sequence of steps illustratedin FIG. 1 at a substantially uniform velocity, for example about 2()yards per minute. The velocity may be greater or less if desired, butgreater velocities require correspondingly larger apparatus in order toachieve the same residence times in each of the various steps. Minorvariations in warp velocity occur at different points in the process forreasons to be hereinafter explained.

The warps of cotton yarn are first introduced into a hot water tank 11for boiling out, i.e., removal of any grease and foreign matter which isadhering to the yarn, and are then cooled to about room temperature `in.cold water tank 12. The yarn is then immersed in a mercerization vessel13 containing caustic soda solution. The ternheating perature and theconcentration of the caustic soda solution may be the same as inconventional mercerizing procedures. For example, a typical causticsolution contains about 20% or v25% aqueous of caustic soda and is atapproximately room temperature. It is understood that the temperaturemay be higher or lower and the concentration greater or less inaccordance with usual mercerizing procedures.

The warp of yarn may be washed in dilute aqueous caustic soda in ivessel14 after mercerization. The temperature of this wash solution isgenerally elevated, for example about 140 F.

The sheet of yarn after washing in caustic washing vessel 14 is heatedin first steam heating chamber 15. Steaming in chamber 15 conditions thethread so that impurities therein which are diicult to bleach, such asfragments of seeds and hulls, will be bleached white. The yarn enteringsteaming cham-ber 15 carries with it a small amount of caustic solution,for example about 3% by weight based on the weight of yarn. The amountof caustic can be greater, up to about 6 to 8% of the weight of yarn. Asmall amount of caustic on the yarn as it enters steaming chamber 15 isessential for subsequent receptivity to bleaching, although the amountmay vary widely while obtaining good results.

Steam is supplied to chamber 15 from a source of supply 16. Thetemperature in steam heating chamber 15 may be varied over wide limits.Generally the temperature is between about 180 F. and about 212 F. In atypical operation, the temperature in steam heating chamber 15 ismaintained at about 190 F. to 200 F. The appropriate temperature may bemaintained by the admission of either dry saturated steam or wet steamat atmospheric pressure from steam source 16. In order to prevent thetemperature from going too high, cold water may be admitted as requiredto steam chamber 15 from cold water source 18. Addition of cold watermay be necessary, for example, when forward movement of yarn through theapparatus is temporarily halted for any reason, such as splicing of yarnends from successive warps. The yarn remains in steam heating chamber 15about one minute at 190 to 200 F.

After steaming in first steam heating chamber 15, the yarn is washed ina dilute solution of caustic soda contained in vessel 20. This washingsolution has a concen- 140 F. to 180 F. are advantageous. Theconcentration is preferably about 1% by weight of caustic soda in water;higher or lower concentrations may be used.

The yarn after being washed in caustic wash tank is then immersed in ableaching solution contained in bleaching tank 22. The yarn as it entersbleaching tank 22 has a moisture content of about 80% of saturation,which corresponds to about 0.8 pound of water per pound of dry yarn. Thebleaching solution may be any of the alkaline bleaching solutions knownin the art. For example, the yarn may be bleached in a solution ofhypochlorite in an alkaline medium. The preferred bleaching agentsolution, however, is an aqueous solution of hydrogen peroxide, causticsoda, and sodium silicate. The concentration of hydrogen peroxide isgenerally in the range of about 2% to about 4% of the total weight ofthe solution. Caustic soda in concentrations ranging from about 1% to 2%of the total weight of the solution is also present. In general, thehigher concentrations of caustic soda are used with the higherconcentrations of hydrogen peroxide. The optimum concentration ofbleaching agent can readily be determined by bleaching a sarnple of thematerial to be bleached. -It is lalso desirable, although not essential,to include sodium silicate in the solution. This sodium silicate may bea conventional water glass solution containing approximately 3.3 mols ofSiOz 4 for each mol of NagO. The concentration of sodium silicate ispreferably about 1% to about 4%, a concentration of 2% being typical.

The temperature of the solution in bleaching tank 22 may be in the rangeof about F. up to the boiling point of water. Preferred temperatures areabout to about F. These temperatures are considerably below bleachingtemperatures used heretofore with hydrogen peroxide as the bleachingagent. Generally the art has preferred to maintain the temperature atabout to about F. when using an aqueous alkaline hydrogen peroxide`solution for bleaching.` Alternative ranges for the temperature of anaqueous alkaline solution of hydrogen peroxide, which contains analkaline metal silicate, are about 110 to about 200 F. and about 110 F.to about In addition to the hydrogen peroxide, caustic soda and sodiumsilicate, the bleaching solution may also contain a small amount ofepsom salts (magnesium sulfate), for example, about 1/2 ounce pergallon. It is also desirable to add a chelating agent. Variouscommercial chelating agents are quite satisfactory forthis purpose. Oneof these, lby way of example, diethylenetriaminepentaacetic acid, soldunder the trade name Versenex 80. The epsom salt and the chelating agentare conveniently supplied as aqueous solutions containing one pound pergallon and one pint per gallon respectively.

It is necessary to replenish all constituents of the bleaching solutionto make up for solution carried out on the` yarn. Replacement solutionsare most advantageously supplied continuously, and in such proportionsthat the bleaching solution retains its original composition. Forexample, in the case of 18 warps of cotton yarn each y containing 378yarn ends and passing through the bleaching tank at the rate of 20 yardsper minute, make-up hydrogen peroxide may be added as a 50% aqueoussolution at the rate of 15 gallons per hour. Make-up caustic sodasolution and make-up sodium silicate solution may be added at the ratesof y3 gallons per hour and 4 gallons per hour, respectively, fromsolution tanks 26 and 28, respectively. The make-up caustic solution inthis case contains 50% by weight of NaOH, and the make-up silicatesolution contains 81% by weight of sodium silicate having theapproximate formula Na2O3.3SiO2. The flow rates and concentrationsherein are merely illustrative and may be varied, depending on thedesired concentrations in bleach tank 22 and the rate of liquidcarry-out therefrom.

After the warp of yarn passes through the bleaching tank 22 it enters asecond steam heating chamber 30. At this point the moisture content ofthe yarn is 100% of saturation. Steam heating chamber 30 is maintainedat a temperature of about 212 F., although the temperature may be eithersomewhat higher or lower, as desired. Generally, the temperature insteam heating chamber 30 will be in the range of 212 to 220 F., or thetemperature may be 212 to about 240 F. Live steam, preferably drysaturated steam at 212 F. and l atmosphere pressure, is introduced intosteam heating chamber 30. Wet steam or superheated steam may be used ifdesired. The warp of yarn passes through steam heating chamber 30 in aplurality of passes so as to afford prolonged exposure to the hightemperature of steam. Bleaching agent adheres to the yarn as it enterssteam heating chamber 30. Most of the bleaching action takes place insteam heating chamber 30 due to the elevated temperature prevailingtherein, rather than in bleaching tank 22. While the residence time ofyarn` in steam heating chamber 30 may be varied within wide limits, itis generally found that bleaching times of about 4 to 6 minutes inchamber 30 are sufficient. This is considerably less than the timesrequired for batch bleaching as previously practiced. The residence timeof yarn in chamber 30 must be sufficiently long to insure properbleaching, and at the same time must not be so long as to result indegradation of the cotton. Steam heating chamber 30 may be heated bymeans of an auxiliargtl heater if desired, especially if it is desiredto maintain a temperature above 212 F. at one atmosphere.

A slight elongation of the yarn, usually about 0.5%, takes place as theyarn passes through steaming chamber 30. To maintain the yarn taut, itis necessary to increase the speed of the yarn in an amount proportionalto the amount of elongation. Thus the exit velocity of the yarn as itleaves steaming chamber30 is about 0.5% greater than the entrancevelocity. In the typical case already mentioned where the entrancevelocity is 20 yards per minute, the exit velocity is 20.1 yards perminute.

After steaming in chamber 30, the yarn is washed by passage through aplurality of wash tanks. Typically the wash'tanks include one or morewater wash tanks 32 followed by an acid wash tank 34 in which the yarnis passed through a dilute aqueous acid solution of a suitable acid suchas acetic acid. The yarn after acid washing may be contacted with abluing solution in bluing tank 36, or processed in such other finishingoperations as desired. After any desired bluing and finishing areperformed, the warp of yarn is conveyed to a drier, where the yarn isdried. The yarn ends may then be separated and each individual threadmay be wound to form a package as desired.

The apparatus for carrying out the above described process will now bedescribed14 in greater detail with reference to FIGS. 2 to 8`. Referringfirst of all to FIGS. '2A and 2B, the apparatus includes boiling-outtank 1l, cold water tank 12, mercerization tank 13, caustic wash tank14, first steam treating chamber 15, second caustic wash tank 20,bleaching tank 22, second steam treating chamber 30, water wash tank 32,acid wash tank 34, and bluing tank 36. The warps of yarn pass throughthe elements of the apparatus in the order named, first enteringboilingout tank 11 and finally passing outward from bluing tank 36 to adrier (not shown).

Each of the tanks ll, 12, 13, 14, 20, 32 and 34 includes a plurality ofrollers 42 immersed beneath the liquid surface of the tank, and aplurality of rollers 44 above the liquid surface of the tank. The warpof yarn passes alternately between submerged rollers 42 and overheadrollers 44, so that the yarn passes alternately in and` out of thesolutions contained in each tank. A pair of pinch rolls 46 including afixed lower roll 46a and an upper roll 46b movable toward or away fromlower roll 46a in response to diaphragm actuator 48 is provided for eachof the tanks to control the amount of liquid carryover from that tank tothe next tank in the series. Pinch rolls 46 may be preset to any desiredroll pressure which in turn controls the amount of liquid carried overto the next tank. Diaphragm actuator 48, which may be biased to aconstant predetermined pressure by suitable fluid means such as air,maintains the pair of pinch rolls at the desired operating pressure.Each set of pinch rolls 46 is controlled by a separate diaphragmactuator 48. The lower roll 46a in each set of rolls 46 is motor drivenand the upper roll 46b is an idler.

Boiling-out tank 11, cold water tank 12, mercerization tank 13, andfirst caustic wash tank 14 may be included in a single housing 49 ifdesired. Successive tanks in housing 49 are separated by partitions 50.vSimilarly, in FIG. 2B, which is a continuation of FIG. 2A, water washtank 32, acid wash tank 34, and bluing tank 36 may be included in asingle housing 5l separated by partitions 52.

Referring now to FIGS. 3 and 4, steam heating chamber 15 is preferablyin the shape of a rectangular prism, and includes a plurality of idlerrolls over which the yarn passes. Preferably these rolls are disposed inupper and lower rows 53 and 54 respectively. The yarn is introduced intosteam heating chamber 15 through slot 56 in the bottow wall 58, as maybe seen best in FIG. 5. The entering yarn passes upwardly over the firstof the upper rolls 53, thence downwardly over the first of the lowerrolls 54, thence back and forth alternately over rolls 53 and 54, andfinally passes downwardly through exit opening in bottom wall 58. A.lconduit 61 is provided for', the introduction of steam into heatingchamber 14. n

' Bleaching tank 22, which is best seen in FIG. 6, is. preferably in theform of a rectangular box, made of sheet metal, and having an open top.The tank 22`has exterior side walls 62 and a bottom wall 64 of sheetmetal. A plurality of rollers 66 are provided in tank 22 beneathftheliquid surface for carrying the warp through the tank. Two pairs ofdiaphragm-actuated power driven pinch rolls 67, each including a fixeddriven lower roll 67a and a vertically movable upper idler roll 67bcontrolled by diaphragm actuator 67e and additional idler rollers 68,are located in the air space above bleaching tank 22 (see FIG. 2A). Thewarp passes alternately over a roller66 in bleaching tank 22 and aroller 68 above the bleaching tank, so that the yarn has a plurality ofpasses in and out of the bleaching tank 22. The interior Wall '.70 ofbleaching tank 22 is made of sheet metal and has'a plurality ofupstanding ridges 71 between adjacent rollers 66. The wall 72 isdisposed close to rollers 66 so as to minimize the volume of solutionrequired in bleachingtank 22. The space between wall 70 and side wall 62and bottom wall 64 constitutes a cooling water shell 74. Cooling wateris introduced into shell 74 by inlet 76 and removed through coolingwater outlet 78.

Bleaching tank 22 also includes a cylindrical .sleeve 80 defining amixing chamber near one end of the tank. In the water inlet pipe 82 forthe introduction of make-upY or process water, a second inlet pipe 84for the introduction ofcaustic soda and sodium silicate solutions, and athird inlet pipe 86 for the introduction of hydrogen'peroxide solution,lead to the mixing chamber contained in sleeve 80. The caustic sodasolution is conveyed ito` mixing chamber through suitable piping 88from=castic soda tank 26, and sodium silicate solution is conveyed tomixing chamber 80 through piping 90 from sodium silicate tank 28. Piping88 and 90 come together at mixing funnel 91 which feeds mixed causticand silicate solutions into mixing chamber 80 through .pipe 84. Forconvenience, the caustic soda tank 26 and the sodium silicate tank28 maybe included in a single housing 92 which includes an internal partition94 separating tanks 26 and 28.'.H-ydrogen peroxide is introduced throughpiping 96 into inlet pipe 86 and thence into mixing chamber 80.

Bleaching tank 22 includes a recirculation system which comprises anoutlet pipe 98 leading from tank 22 a`short distance below mixingchamber 80, a recirculation'pump 100, and a main 102 having a pluralityof inlets Vy10411, 104b, 104e` and 104d leading to spaced points at thebottom of bleaching tank 22. Preferably these inlets lead intoindividual sections of the bleaching tank 22 whichV are separated by theconvolutions in wall 72. Main 102 also serves as a drain when it isdesired to empty the bleaching tank 22 of bleaching solution. Ordinarilyduring operation of bleaching tank 22, it is not necessary to remove'any liquid therefrom, since a substantial volume of liquid is carriedout of bleaching tank 22 by the yarn. The makeup caustic soda, sodiumsilicate, hydrogen` peroxide and water introduced into mixing chamber 80and thence into bleaching tank 22 make up for losses of liquid which arecarried out by the yarn. According to a typical embodiment, the make-upwater volume is 15 gallons per-ihour, and the volumes of caustic sodasolution, sodium silicate solution, and hydrogen peroxide solution are3"-gallons per hour, 4 gallons per hour, and 15 gallons per hour,respectively. The recirculation pump 100 in this same ernbodiment shouldbe able to handle liquid volumes of l0 gallons lper minute. Of course,it is understood thatill of these figures are merely illustrative, andthe size `of: the bleaching tank, which is determined by the size oftheE apparatus as a whole, may be varied at will. f -1 The feed lines88, and 96 for caustic, sodiumsilicate, and hydrogen peroxide,respectively, contain pumps 110, 112 and 114, respectively, which aredriven by a gang drive from a single alternating Current motor 116; A

switch 118 is placed in AC line 120 leading to motor 116 so that pumps110, 112 and 114 will ordinarily be shut down in the event that thedriven rolls in mercerizer 13 are stopped. To this end, switch 118 iscontrolled by a solenoid 122. Energzation of solenoid 122 is controlledby lpower line 124 which includes a normally open relay 126 which isclosed whenever the motor to the powerdriven rolls 46a in pinch rolls 46are in use, and a manually operated override relay 128 for permittingenergization of solenoid 122 when the power-driven rolls 46a are shutdown. When the pinch rolls 46a are in operation, relay 126 is closed andrelay 128 open, causing solenoid 122 to be energized. When these rollsare shut down, both relays 126 and 128 are open unless relay 128 ismanually closed. In this way pumps 110, 112 and 114 are automaticallyshut down when the mercerizer pinch rolls are not in operation, unlessrelay 128 is manually closed in order to permit override operation.

The water supplied to pipe 82 is controlled by a diaphragm-operatedvalve 130 wherein control of the diaphragm is effected by an air supply132 under pressure. This air supply is controlled by a solenoid valve134 which is in parallel with solenoid 122 in power line 124. Thus, whenpinch rolls 46 above the mercerizer 13 are in operation, Ipower line 124is energized, valve 134 is opened, supplying air through line 132 to thediaphragm in valve 130 and thus causing valve 130 to be opening for theadmission of process water. Likewise, process water is shut olf 4whendriven rolls 46a are shut down.

The rate of cooling water supplied into shell 74 is controlled by atemperature controller 136 which is responsive to the temperature ofsolution in bleaching tank 22. Controller 136 operates a valve 138 inthe cooling water supply line 140, leaving the cooling water inlet 76 inaccordance with the bleaching tank solution temperature.

The structure of the second steam heating chamber 30 is best shown inFIG. 7. Steam heating chamber 30 is generally rectangular in shape,having housing side wal-ls 140 including access doors 142 in at leastone of said walls for permitting access to the interior, a bottom wall144, a -top wall 146, and an inlet chute 148 adjacent one end wall forthe admission of the continuously traveling warp of yarn. Inlet chute148 preferably extends below bottom wall 144 and includes a pair ofrubber or plastic flaps 149 (see FIG. 9) and an idler roller 150 fordirecting the warp of yarn from a horizontal direction to an upwardvertical direction. A plurality of plate heaters 149 having steamheating coils (not shown) and mounted on the inside walls of chamber 30permit superheating of the steam therein. Steam heating chamber 30includes a plurality of rolls for conveying the warp of yarn through thechamber. This plurality of rolls includes a plurality of driven rol-ls152 arranged in a row adjacent the top wall 146, and a plurality ofidler rolls 154 arranged in a second row adjacent bottom wall 144. Thechamber 30 also includes an exit opening 156 for the warp of yar-nleaving chamber 30.

The speed of the yarn increases by a slight amount, usually about 0.5%,as it passes through chamber 30. Since the yarn must be maintained tautat all times in chamber 30 without slip between the yarn and drivenrolls 152, it is necessary to drive rolls 152 at different speeds sothat each roll travels at the same speed as that of the yarn passingthereover. To this end, a clutch drive mechanism 158, illustrated inFIG. 8, is provided.

Referring now to FIG. 8, roll 152 has a pair of shaft portions 160 and`162 progressively smaller diameter and integral and concentric withroll 1'52. Shaft 162 is driven by a chain drive mechanism (not shown)through sprocket 163 and sleeve 164 welded thereto and surrounding shaft162. Bearing 166 is interposed between sleeve 164 and shaft 162. Theclutch mechanism also includes a washer 168 having ange 170 thereon.Washer 168 is maintained in driving relationship with shaft 160 by meansof dowel pin 172. A pair of axially displaced thrust washers 174 and 176are disposed at either end of sleeve 164. Thrust washer 174 bearsagainst washer 168 so as to transmit motion from sleeve 164 to washer168 and thence to shaft 160. A retaining sleeve 178 is located axiallyoutwardly from sleeve 164 and bea-rs against washer 176. Key 179 onshaft 162 and a mating keyway in sleeve 178 cause sleeve 178 and shaft162 to rotate as a unit. A spring-pressed washer 184 holds the entireclutch drive mechanism 158 in place. Shaft 162 has a internallyscrewth-readed bore 180 at its outer end which receives externallyscrew-threaded bolt 182. The assembly includes washer 184 which isspring-pressed against retaining sleeve 178 by compression spring 186.-It will thus be apparent that roll 1'52, shafts 160 and 162, andretaining sleeve 178 all rotate as a unit, but that sleeve 164 mayrotate at a different speed from the rest of the unit. This provides afriction drive transmitting power from sprocket 163 to roller 152,permitting shaft 162 to slip with respect to sleeve 164. The amount ofslip between sleeve 164 and shaft 162 is controlled by turning screw182. In this way the axial pressure between sleeve 164 and thrustwashers 174 and 176 may be varied depending on the amount of slipdesired.

Referring again to PIG. 2B, hot water wash tank 32 is partitioned bypartition 187 to provide a pair of side-byside wash tanks 32a and 32b.Water is withdrawn from the bottom of tank 32a via conduit 188 near theend of tank 32a where warp 10 of yarn first enters the tank. This wateris recirculated by pump 189 through heater 190 and header 191 to sprays192 and 193, which direct hot water against the yarn 10 to wash thesame.

A second recirculation pump 194 withdraws hot wash water Ifrom thebottoms of tanks 32a and 32b via conduit 196 an-d returns the waterthrough conduit 198 and header 200 to sprays 202 and 204 which directwater against yarn 10. Water is also withdrawn from tank 32b throughline 205 by reci-rculation pump 206 and returned through conduit 208 tospray 209 which directs hot water against warp 10 of yarn.

Fresh water supplied lthrough conduit 210 is heated in two-stage heater212 by overow water from tank 32a, which is piped to heater 212 throughpipeline 214. The hot water is further heated in a second two-stageheater 216 to about 190 F., and .then is piped to hot w-ater spray 218which directs hot water against yarn 10. Spray 218 has an alternativehot water supply conduit 220.

-In addition to the aforedescribed recirculation systems, tanks 32a and32b also have drain conduits 221 and 222 respectively.

Acid w-ash tank 34 has a recirculation system for washing the yarn withdilute aqueous acid. This system includes withdrawal conduit 224 leadingfrom the bottom of tank 34, pump 226, re'tu-rn line 228 having heater230 therein, and acid spray nozzle 232 at the end of return line 228directing dilute acid against warp 10. Acid wash tank 34 also has adrain conduit 234.

Chemical treat-ment tank 36 for supplying bluing or other desiredfinishing chemical, is divided into two separate compartments 36a and36b by partition 235. This tank has a trough 236 on one end partition 52in compartment 36a for adding bluing or other finishing chemical. Thischemical is mixed in trough 236 with solution from tank 36. Theresulting solution is withdrawn from trough 236 by recirculating pump238, which reintroduces the solution linto compartment 36b via line 240after heating in heater 242. Drain conduits 244 and 246 lead from thebottom of compartments 36a and 36b respectively.

After finishing in tank 36, yarn 10 is withdrawn for drying.

Example 1 A warp of yarn is made up by bringing 378 ends of cotton yarntogether after the yarns have been individually passed through a llameto remove lint and fuzz. The yarn ends are broughttogether insidc-by-side parallel relationship with all of the yarn ends lying in asingle phase. Eighteen warps made in this manner are continuouslyadvanced in parallel side-by-side relationship through the sequence ofsteps illustrated in FIG. 1 of the drawing, using the apparatus shown inFIG. 2. The velocity of the yarn is 20 yards per minute throughout theprocess from the beginning until the yarn reaches steam heating chamber30. The velocity increases to about 20.1 yards per minute in steamheating chamber 30, and remains at this level throughout the remainderof the process.

The sheet of yarn 10 is li-rst contacted with boiling water inboiling-out tank l1 toremove grease and impurities. The yarn is thencooled to about room temperature in cold water tank 12, and is thenpassed into mercerizing tank 13 containing an aqueous 23% caustic sodasolution at room temperature. The yarn is then washed in caustic washtank 14 containing an aqueous solution of 7% to 9% by weight of causticsoda. The pressure of rolls 46 through which the warp of yarn is passedafter it leaves caustic wash tank 13 is set so that the yarn contains 3%by weight of caustic solution as it enters first steaming chamber 15.The yarn passes through steaming chamber l in a plurality of passes. Wetsteam is continuously supplied to steaming chamber 15, and thetemperature in that chamber is maintained at 190 F. to 200 F. Theresidence time of yarn in steaming chamber 14 is approximately oneminute. The yarn is then passed through a second caustic wash solutionin tank 20. This caustic wash solution also contains 1% by weight ofcaustic soda and is at a temperature of 140 F. to 180 F.

After caustic washing in tank 20, the yarn enters bleaching tank 22. Theyam is contacted in bleaching tank 22 with a bleaching solutioncontaining 4% by weight of hydrogen peroxide, 1% by weight of causticsoda, 2% by weight of sodium silicate (water glass, Na2O3.3SiO2), leounce per gallon of epsom salts (magnesium sulfate), and l/z ounce pergallon of diethylenetriaminepentaacetic acid chelating agent (Versenex80). The temperature in bleaching tank 22 is 120 F. Makeup solutions arecontinuously supplied to bleaching tank 22 from hydrogen peroxidestorage tank 24 containing 50% aqueous hydrogen peroxide, caustic sodatank 26 containing 50% by weight of caustic soda, sodium silicatesolution tank 28 containing 81% lby weight of sodium silicate (waterglass) having the approximate formula Na2O-3.3SiO2, epsom salts make-uptank containingl pound of epsom salts per gallon of water, and chelatingagent make-up tank containing 1 pint of Versenex 80 per gallon of water.The liow rates of these make-up solutions in gallons per hour are asfollows:

The total amount of make-up solution is approximately equal to theamount of solution carried out by the yarn.

From bleaching tank 22 the yarn goes to second steaming chamber 30. Drysaturated steam is introduced into this chamber at 212 F. and 1atmosphere, and the steam is superheated to about 218 F. by means ofsteam heaters within chamber 30. The speed of the yarn as it enters is20 yards per minute. The yarn passes alternately up and down through anumber of passes in chamber 30, and is kept under tension at all times.Due to the tension and the high temperature in chamber 30, the velocityincreases by about 0.5% to 20.1yards-perminute at the exit. The yarnpasses alternately over a driven roll 152 and an idler roll 154. Theroll speed of driven rolls 152 progressively increases as the warp ofyarn advances through chamber 30,

so that 'there is no slip between the yarn and any of the 10 rolls. Theresidencetime of yarn in chamber 30 is approximately 5 minutes.

The yarn upon leaving second steaming chamber 30 is washed with hotwater at 190 F. in water wash tanks 32 and 32a, and then is contactedwith dilute aqueous acetic acid at a temperature of about 140 F. to 160F. in acid wash tank 34'.l After. acid washing, the yarn is contactedwith a bluing agent in bluing tank 36, which is maintained at 160 F.From vbluing tank 36 the yarn passes through a drier. After drying, theyarn is taken up on a pallet.

Example 2 The process of Example 1 is repeated except that theconcentration of hydrogen peroxide in bleaching tank 22 is 2V: The owrate of hydrogen peroxide from storage tank 24 to bleaching tank 22 isabout 9.5 gallons per hour.

While one embodiment of the invention has been shown and describedherein it is to be understood that changes and additions may be made bythose skilled in the art without departing from the scope and spirit ofthe invention.

I claim:

l. A process for rapid bleaching of cotton yarn which comprises thesteps of forming a warp of yarn, contacting said warp with an aqueouscaustic alkaline solution, steaming the causticized yarn, contactingsaid yarn with a bleaching agent in an alkaline medium, steaming theyarn with bleaching agent adhering thereto, and neutralizing the excessalkali adhering to said yarn with dilute aqueous acid.

2. A process for continuously mercerizing and bleaching cotton yarnwhich comprises the steps of forming a warp of yarn ends, and, whilesaid warp is continuously advancing, contacting said warp with anaqueoust caustic alkaline solution, steaming said warp, contacting saidwarp with an aqueous alkaline solution of a lbleaching agent, steamingthe warp with ble-aching agent adhering thereto, and neutralizing thealkali adhering to said yarn with dilute aqueous acid.

3. A process for continuously mercerizing and bleaching cotton yarnwhich comprises the steps of forming a Warp of yarn ends, and, whilesaid warp is continuously advancing, boiling out the warp to removeforeign inatter, contacting said warp with an aqueous caustic alkalinesolution, steaming said warp, washing the warp in aqueous causticalkali, contacting said warp with an aqueous alkaline solution of ableaching agent, steaming the warp lwith bleaching agent adheringthereto, and neutralizing the alkali adhering to said yarn with diluteaqueous acid.`

4. A process according to claim 3 wherein the first-mentioned steamingis carried out at a temperature of about 180 to 212 F. l

5. A process according to claim 3 wherein the second mentioned steamingis carried out at a temperature of g about 212 F.

6. A process according to claim 3 wherein the bleaching agent ishydrogen peroxide.

7. The process according to claim 6 wherein theaqueous alkaline solutionof hydrogen peroxide also contains sodium silicate. 'p

8. A process according to claim 7 wherein the temperature of saidaqueous alkaline solution of hydrogen peroxide is about to about 120 F.

9. A process according to claim 7 wherein the temperature of saidaqueous alkaline solution of hydrogen peroxide is about 110 to about 160F.

10. In a process for mercerization and bleaching of cotton yarn whereina warp of said yarn is contacted with an aqueous caustic solution, theimprovement comprising the Asteps of,

(a) steaming said warp at a temperature below the boiling point of watersubsequent to contacting of said yarn with said caustic solution,

(b) contacting said warp with a Ibleaching agent while alkali adheres tothe yarn, f'

(c) steaming the warp after contact with said bleaching 1l 12 -agent ata temperature not less than the boiling References Cited P011 0f Waterald UNITED STATES PATENTS (d) washing the warp with acid to removealkali adhering to said warp. 11. The process of claim 3, wherein saidwarp ad- 5 vances at a substantially uniform velocity.

12. The process of claim 10, in which the warp is passed LEON D' ROSDOLPrimary Exammer' through each of said steps at a substantially uniformM. WEINBLA'IT, Assistant Examiner. velocity.

1,630,786 5/1927 Conrad 8-101 3,280,039 10/ 1966 Smolens 252-103 XUNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No3,370,911 February 27, 1968 Thomas E. Westall ppears in the abovenumbered pat- It is hereby certified that error a aid Letters Patentshould read as ent requiring correction and that the s corrected below.

l Column 7, line 27, for "opening" read opened column 9 line 3, for"phase" read plane Signed and sealed this 6th day of May 1969.

(SEAL) Attest: Edward M. Fletcher, Jr. W2(

Attesting Officer d Commissioner of Patents

